Hi Ted,
Some tips:
> invlist_negate [] = [0]
> invlist_negate (0:xs) = xs
> invlist_negate xs = 0:xs
You are doing this for generic Num instances, so 0 probably isn't the lower bound. Haskell has another type class for this: Bounded. Then you can use minBound instead of 0. Also the first line is just a special case of the last one.
invlist_negate :: (Bounded a, Num a) => [a] -> [a]
invlist_negate (minBound : xs) = xs
invlist_negate xs = minBound : xs
Try doing invlist_member together with a function invlist_notMember (just like there is notElem for lists), I think that would clean things up a bit.
Keep on going, there's lots of fun ahead!
greetings,
Sjoerd
--
Sjoerd Visscher
sjoerd at w3future.com